Optically aligned pulse oximetry sensor and technique for using the same

ABSTRACT

A physiological sensor is provided that includes an emitter and detector disposed on a frame such that the emitter and detector define an optical axis. The frame includes one or more pair of flexible elements disposed generally symmetric relative to the optical axis. In one embodiment, the emitter and detector remain aligned when moved relative to one another along the optical axis.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to pulse oximetry and, moreparticularly, to sensors used for pulse oximetry.

2. Description of the Related Art

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present invention,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

In the field of medicine, doctors often desire to monitor certainphysiological characteristics of their patients. Accordingly, a widevariety of devices have been developed for monitoring physiologicalcharacteristics. Such devices provide doctors and other healthcarepersonnel with the information they need to provide the best possiblehealthcare for their patients. As a result, such monitoring devices havebecome an indispensable part of modern medicine.

One technique for monitoring certain physiological characteristics of apatient is commonly referred to as pulse oximetry, and the devices builtbased upon pulse oximetry techniques are commonly referred to as pulseoximeters. Pulse oximetry may be used to measure various blood flowcharacteristics, such as the blood-oxygen saturation of hemoglobin inarterial blood, the volume of individual blood pulsations supplying thetissue, and/or the rate of blood pulsations corresponding to eachheartbeat of a patient.

Pulse oximeters typically utilize a non-invasive sensor that is placedon or against a patient's tissue that is well perfused with blood, suchas a patient's finger, toe, or earlobe. The pulse oximeter sensor emitslight and photoelectrically senses the absorption and/or scattering ofthe light after passage through the perfused tissue. The data collectedby the sensor may then be used to calculate one or more of the abovephysiological characteristics based upon the absorption or scattering ofthe light. More specifically, the emitted light is typically selected tobe of one or more wavelengths that are absorbed or scattered in anamount related to the presence of oxygenated versus de-oxygenatedhemoglobin in the blood. The amount of light absorbed and/or scatteredmay then be used to estimate the amount of the oxygen in the tissueusing various algorithms.

In many instances, it may be desirable to employ, for cost and/orconvenience, a pulse oximeter sensor that is reusable. Such reusablesensors, however, should fit snugly enough that incidental patientmotion will not dislodge or move the sensor yet not so tight that normalblood flow is disrupted, which may interfere with pulse oximetrymeasurements. Such a conforming fit may be difficult to achieve over arange of patient physiologies without adjustment or excessive attentionon the part of medical personnel. In addition, for transmission-typepulse oximetry sensors (in which an emitter and detector are provided onopposite sides of the finger or toe) it may be difficult to maintain thedesired alignment of optical components while obtaining a conformingfit. For example, it may be desirable to maintain the emitter anddetector along a common axis, however, such alignment may be difficultto achieve or maintain while adjusting the sensor and its constituentcomponents to fit a patient physiology.

SUMMARY

Certain aspects commensurate in scope with the originally claimedinvention are set forth below. It should be understood that theseaspects are presented merely to provide the reader with a brief summaryof certain forms of the invention might take and that these aspects arenot intended to limit the scope of the invention. Indeed, the inventionmay encompass a variety of aspects that may not be set forth below.

There is provided a sensor assembly that includes: a frame comprisingone or more pair of flexible elements disposed substantially symmetricrelative to an optical axis; at least two optical components disposed onthe frame along the optical axis; and a covering provided over at leastpart of the frame and the at least two optical components.

There is provided a sensor assembly that includes: a frame; an emitterand a detector housed on the frame along an optical axis, wherein theemitter and the detector are configured to move relative to one anotherwhile remaining aligned along the optical axis; and a covering providedover the frame, the emitter, and the detector.

There is provided a method of manufacturing a sensor that includes:situating an emitter and a detector on a frame, wherein the framecomprises one or more pair of flexible elements disposed substantiallysymmetric relative to an optical axis upon which the emitter and thedetector are situated; and coating the frame with a coating material toform a sensor assembly.

There is provided a method for acquiring physiological data thatincludes: emitting two or more wavelengths of light from an emitter of asensor assembly disposed on a patient; detecting transmitted orreflected light using a photodetector of the sensor assembly, whereinthe emitter and the photodetector are maintained in optical alignmentwith one another along an optical axis by one or more pair of flexibleelements of the sensor assembly, wherein the one or more pair offlexible elements are disposed symmetrical to the optical axis; anddetermining a physiological parameter based on the detected light.

There is provided a method of manufacturing a sensor body that includes:coating a frame with a coating material to form a sensor body, whereinthe frame comprises one or more pair of flexible elements disposedsubstantially symmetric relative to an optical axis defined by anemitter housing and a detector housing of the frame.

There is provided a sensor body, that includes: a frame comprising oneor more pair of flexible elements disposed substantially symmetricrelative to an optical axis defined by an emitter housing and a detectorhousing of the frame; and a covering provided over the frame.

There is provided a sensor body, that includes: a frame comprising anemitter housing and a detector housing which define an optical axis,wherein the emitter housing and the detector housing are configured tomove relative to one another while remaining aligned along the opticalaxis; and a covering provided over the frame to form a sensor assembly.

There is provided a frame of a sensor, that includes: at least twooptical component housings defining an optical axis; and one or morepair of flexible elements disposed substantially symmetric relative tothe optical axis.

There is provided a frame of a sensor, that includes: an emitter housingand a detector housing which define an optical axis, wherein the emitterhousing and the detector housing are configured to move relative to oneanother while remaining aligned along optical axis.

There is provided a method for manufacturing a frame of a sensor, thatincludes: forming at least two optical component housings of a frame ofa sensor such that the at least two optical component housings define anoptical axis; and providing one or more pair of flexible elements on theframe disposed substantially symmetric relative to the optical axis.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the invention may become apparent upon reading thefollowing detailed description and upon reference to the drawings inwhich:

FIG. 1 illustrates a physiological monitoring system coupled to amulti-parameter patient monitor and a patient sensor, in accordance withaspects of the present technique;

FIG. 2 illustrates a perspective view of one configuration of aninternal frame for use in a patient sensor, in accordance with aspectsof the present technique;

FIG. 3 illustrates the internal frame of FIG. 2 in an expandedconfiguration;

FIG. 4 illustrates the internal frame of FIG. 2 in a collapsedconfiguration;

FIG. 5 illustrates a perspective view of a covered patient sensor basedupon the internal frame of FIG. 2;

FIG. 6 illustrates a perspective view of another configuration of aninternal frame for use in a patient sensor, in accordance with aspectsof the present technique;

FIG. 7 illustrates the internal frame of FIG. 6 in an expandedconfiguration;

FIG. 8 illustrates the internal frame of FIG. 6 in a collapsedconfiguration;

FIG. 9 illustrates a perspective view of a covered patient sensor basedupon the internal frame of FIG. 6;

FIG. 10 illustrates a perspective view of a further configuration of aninternal frame for use in a patient sensor, in accordance with aspectsof the present technique;

FIG. 11 illustrates the internal frame of FIG. 10 in an expandedconfiguration;

FIG. 12 illustrates the internal frame of FIG. 10 in a collapsedconfiguration; and

FIG. 13 illustrates a perspective view of a covered patient sensor basedupon the internal frame of FIG. 10.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

It is desirable to provide a comfortable and conformable reusablepatient sensor that is easily cleaned and that maintains alignmentbetween optical components. In accordance with some aspects of thepresent technique, a reusable patient sensor is provided that includes aflexible frame, such as a framework incorporating living hinges, pinhinges, bar links, bending beams, and so forth, which allows the patientsensor to conform to fingers or toes of varying sizes while maintainingalignment of the optical components.

Prior to discussing such exemplary sensors in detail, it should beappreciated that such sensors are typically designed for use with apatient monitoring system. For example, referring now to FIG. 1, asensor 10 according to the present invention may be used in conjunctionwith a patient monitor 12. In the depicted embodiment, a cable 14connects the sensor 10 to the patient monitor 12. As will be appreciatedby those of ordinary skill in the art, the sensor 10 and/or the cable 14may include or incorporate one or more integrated circuit devices orelectrical devices, such as a memory, processor chip, or resistor thatmay facilitate or enhance communication between the sensor 10 and thepatient monitor 12. Likewise the cable 14 may be an adaptor cable, withor without an integrated circuit or electrical device, for facilitatingcommunication between the sensor 10 and various types of monitors,including older or newer versions of the patient monitor 12 or otherphysiological monitors. In other embodiments, the sensor 10 and thepatient monitor 12 may communicate via wireless means, such as usingradio, infrared, or optical signals. In such embodiments, a transmissiondevice (not shown) may be connected to the sensor 10 to facilitatewireless transmission between the sensor 10 and the patient monitor 12.As will be appreciated by those of ordinary skill in the art, the cable14 (or corresponding wireless transmissions) are typically used totransmit control or timing signals from the monitor 12 to the sensor 10and/or to transmit acquired data from the sensor 10 to the monitor 12.In some embodiments, however, the cable 14 may be an optical fiber thatallows optical signals to be conducted between the monitor 12 and thesensor 10.

In one embodiment, the patient monitor 12 may be a suitable pulseoximeter, such as those available from Nellcor Puritan Bennett Inc. Inother embodiments, the patient monitor 12 may be a monitor suitable formeasuring tissue water fractions, or other body fluid related metrics,using spectrophotometric or other techniques. Furthermore, the monitor12 may be a multi-purpose monitor suitable for performing pulse oximetryand measurement of tissue water fraction, or other combinations ofphysiological and/or biochemical monitoring processes, using dataacquired via the sensor 10. Furthermore, to upgrade conventionalmonitoring functions provided by the monitor 12 to provide additionalfunctions, the patient monitor 12 may be coupled to a multi-parameterpatient monitor 16 via a cable 18 connected to a sensor input portand/or via a cable 20 connected to a digital communication port.

The sensor 10, in the example depicted in FIG. 1, may be covered toprovide a unitary or enclosed assembly. Such covering, however, isoptional. The sensor 10, includes an emitter 22 and a detector 24 whichmay be of any suitable type. For example, the emitter 22 may be one ormore light emitting diodes adapted to transmit one or more wavelengthsof light, such as in the red to infrared range, and the detector 24 maybe a photodetector, such as a silicon photodiode package, selected toreceive light in the range emitted from the emitter 22. In the depictedembodiment, the sensor 10 is coupled to a cable 14 that is responsiblefor transmitting electrical and/or optical signals to and from theemitter 22 and detector 24 of the sensor 10. The cable 14 may bepermanently coupled to the sensor 10, or it may be removably coupled tothe sensor 10—the latter alternative being more useful and costefficient in situations where the sensor 10 is disposable.

The sensor 10 described above is generally configured for use as a“transmission type” sensor for use in spectrophotometric applications.As will be appreciated by those of ordinary skill in the art, however,such discussion is merely exemplary and is not intended to limit thescope of the present technique. Transmission type sensors include anemitter and detector that are typically placed on opposing sides of thesensor site. If the sensor site is a fingertip, for example, the sensor10 is positioned over the patient's fingertip such that the emitter anddetector lie on either side of the patient's nail bed. For example, thesensor 10 is positioned so that the emitter is located on the patient'sfingernail and the detector is located opposite the emitter on thepatient's finger pad. During operation, the emitter shines one or morewavelengths of light through the patient's fingertip, or other tissue,and the light received by the detector is processed to determine variousphysiological characteristics of the patient.

For pulse oximetry applications using transmission type sensors theoxygen saturation of the patient's arterial blood may be determinedusing two or more wavelengths of light, most commonly red and nearinfrared wavelengths. Similarly, in other applications a tissue waterfraction (or other body fluid related metric) or a concentration of oneor more biochemical components in an aqueous environment may be measuredusing two or more wavelengths of light, most commonly near infraredwavelengths between about 1,000 nm to about 2,500 nm. It should beunderstood that, as used herein, the term “light” may refer to one ormore of infrared, visible, ultraviolet, or even X-ray electromagneticradiation, and may also include any wavelength within the infrared,visible, ultraviolet, or X-ray spectra.

Pulse oximetry and other spectrophotometric sensors are typically placedon a patient in a location conducive to measurement of the desiredphysiological parameters. For example, pulse oximetry sensors aretypically placed on a patient in a location that is normally perfusedwith arterial blood to facilitate measurement of the desired bloodcharacteristics, such as arterial oxygen saturation measurement (SaO₂).Common pulse oximetry sensor sites include a patient's fingertips, toes,forehead, or earlobes. Regardless of the placement of the sensor 10, thereliability of the pulse oximetry measurement is related to the accuratedetection of transmitted light that has passed through the perfusedtissue and has not been inappropriately supplemented by outside lightsources or modulated by subdermal anatomic structures. Suchinappropriate supplementation and/or modulation of the light transmittedby the sensor can cause variability in the resulting pulse oximetrymeasurements.

Referring now to FIGS. 2-13, the sensor 10 is discussed in greaterdetail. For example, in FIGS. 2-4, a first configuration 28 of anexemplary frame 30 for a sensor 10 is depicted. Such a frame 30 mayprovide an internal structure that defines the general shape of thesensor 10 when covered, such as by overmolding, to form the patientsensor 10. In such an embodiment, the frame 30 may provide a generalstructure and range of motion for the patient sensor 10 while thecovering may provide a surface area which contacts the patient and mayprotect the frame 30 and optical components of the patient sensor 10. Inview of the various structural and motion functions performed by theframe 30, different structures or regions of the frame 30 may havesimilar or different rigidities or other mechanical properties.

The frame 30 may include various structural features such as a cableguide through which a cable, such as an electrical or optical cable, maypass to connect to the electrical or optical conductors attached to theemitter 22 and/or detector 24 upon assembly. Likewise, the frame 30 mayinclude component housings, such as the emitter housing 34 and detectorhousing 36. In addition, the frame 30 may include flexible components orelements 38, such as living hinges, pin hinges, bar links, bendingbeams, and so forth, which facilitate the motion of the emitter housing34 and/or the detector housing 36 relative to one another.

In certain embodiments, the frame 30 is constructed, in whole or inpart, from polymeric materials, such as thermoplastics, capable ofproviding a suitable rigidity or semi-rigidity for the differentportions of the frame 30. Examples of such suitable materials includepolyurethane, polypropylene, and nylon, though other polymeric materialsmay also be suitable. In other embodiments, the frame 30 is constructed,in whole or in part, from other suitably rigid or semi-rigid materialsthat provide the desired support and flexibility, such as stainlesssteel, aluminum, magnesium, graphite, fiberglass, or other metals,alloys, or compositions that are sufficiently ductile and/or strong. Forexample, metals, alloys, or compositions that are suitable fordiecasting, sintering, lost wax casting, stamping and forming, and othermetal or composition fabrication processes may be used to construct theframe 30.

In addition, the frame 30 may be constructed as an integral structure oras a composite structure. For example, in one embodiment, the frame 30may be constructed as a single piece from a single material or fromdifferent materials. Alternatively, the frame 30 may be constructed orassembled as a composite structure from two or more parts that areseparately formed. In such embodiments, the different parts may beformed from the same or different materials. For example, inimplementations where different parts are formed from differentmaterials, each part may be constructed from a material having suitablemechanical and/or chemical properties for that part. The different partsmay then be joined or fitted together to form the frame 30, such as by asnap fitting process, ultrasonic welding, heat staking or by applicationof an adhesive or mechanical fastener.

For example, the flexible elements 38, such as living hinges, pinhinges, bar links, bending beams, and so forth, may be constructed fromthe same materials and/or from different materials than the remainder ofthe frame 30. Furthermore, the flexible elements 38 may be formedintegrally with the remainder of the frame 30. For example, in oneembodiment, the frame 30 may be molded from polymeric materials as onepiece, with the flexible elements 38 formed as living hinges molded fromthe polymeric material. Alternatively, some or all of the flexibleelements 38 may be molded or formed as separate pieces that are attachedto the remainder of the frame structure. In such embodiments, theflexible elements 38 may be formed from the same or different materialsand the remainder of the frame 30 and may serve to hold differentportions of the frame structure together. For example, in an embodimentin which the flexible elements 38 are pin hinges, the frame sides 42 maybe formed from polymeric materials and may include annular structuresalong their edges that are complementary to the annular structures of anadjacent frame side 42. In such an embodiment, a pin, such as a metalpin, may be fitted through the annular structures of two adjacent framesides 42, thereby forming an attachment and a hinge upon which theattached frame sides 42 may be moved. As will be appreciated by those ofordinary skill in the art, other suitable hinge and/or attachmenttechniques may also be applicable to construct the frame 30.

Furthermore, the frame 30 may be molded, formed, or constructed in adifferent configuration than the final sensor configuration. Forexample, the frame 30 for use in the sensor 10 may be initially formed,from one or more pieces, in a generally open, or flat, configurationcompared to the relatively closed configuration of the frame 30 whenfolded to form the sensor 10. In such embodiments, the frame 30 may beformed generally open or planar and then folded or bent, such as at theflexible regions 38, into the closed configuration associated with thesensor 10. A covering may be applied, such as by overmolding, prior toor subsequent to folding or bending the frame 30 from the openconfiguration to the closed configuration. In such an embodiment, theframe 30 may be secured together as described above, such as via a snapfitting process or via other techniques suitable for attaching therespective portions of the frame 30 including ultrasonic welding, heatstaking or by application of an adhesive or mechanical fastener.

In the example depicted in FIGS. 2-4, a first configuration 28 of theframe 30 is provided. In the first configuration 28, the flexibleregions 38 are provided in pairs that are symmetric about a verticalplace that coincides with the optical axis 44. The paired, symmetricflexible regions 38 allow lineal expansion and/or contraction along theoptical axis 44, thereby maintaining optical alignment of the emitter 22and detector 24 as the frame 30 expands or collapses to conformably fita patient's digit. In addition, the flexible regions 38 may allowlateral expansion (i.e., transverse to the optical axis) of the frame 30to provide a laterally conforming fit to differently sized fingers andtoes.

For example, referring now to FIG. 3, the first configuration 28 of FIG.2 is depicted as expanded along the optical axis 44 between the emitter22 and detector 24, such as to accommodate a large finger or toe needinggreater vertical space. The paired, symmetric flexible regions 38constrain the range of motion of the emitter 22 and detector 24 tolinear motion along the optical axis 44, thereby maintaining the emitter22 and detector 24 in alignment despite there motion relative to oneanother. Similarly, referring now to FIG. 4, the first configuration 28is depicted as collapsed along the optical axis 44, such as toaccommodate a smaller finger or toe, while maintaining alignment of theemitter 22 and detector 24 along the optical axis 44.

As noted above, in certain embodiments of the present technique, theframe 30 (such as the first configuration 28 of the frame 30) may becovered to form a unitary or integral sensor assembly or sensor body, asdepicted in FIG. 5. Such covered embodiments may result in a sensorassembly in which the internal frame 30 is completely or substantiallycovered by a covering material 50. In embodiments in which the internalframe 30 is formed or molded as a relatively open or flat structure, thecovering process may be performed prior to or subsequent to bending theinternal frame 30 into the closed configuration.

For example, the sensor 10 may be formed by an injection moldingprocess. In one example of such a process the internal frame 30 may bepositioned within a die or mold of the desired shape for the sensor 10.A molten or otherwise unset overmold material may then be injected intothe die or mold. For example, in one implementation, a moltenthermoplastic elastomer at between about 400° F. to about 450° F. isinjected into the mold. The coating material may then be set, such as bycooling for one or more minutes or by chemical treatment, to form thesensor body about the internal frame 30. In certain embodiments, othersensor components, such as the emitter 22 and/or detector 24, may beattached or inserted into their respective housings or positions on theovermolded sensor body.

Alternatively, the optical components (such as emitter 22 and detector24) and/or conductive structures (such as wires or flex circuits) may beplaced on the internal frame 30 prior to overmolding. The internal frame30 and associated components may then be positioned within a die or moldand overmolded, as previously described. To protect the emitter 22,detector 24, and or other electrical components, conventional techniquesfor protecting such components from excessive temperatures may beemployed. For example, the emitter 22 and/or the detector 24 may includean associated clear window, such as a plastic or crystal window, incontact with the mold to prevent coating 50 from being applied over thewindow. In one embodiment, the material in contact with such windows maybe composed of a material, such as beryllium copper, which prevents theheat of the injection molding process from being conveyed through thewindow to the optical components. For example, in one embodiment, aberyllium copper material initially at about 40° F. is contacted withthe windows associated with the emitter 22 and/or detector 24 to preventcoating of the windows and heat transfer to the respective opticalcomponents.

As will be appreciated by those of ordinary skill in the art, theinjection molding process described herein is merely one technique bywhich the frame 30 may be covered to form a sensor body, with or withoutassociated sensing components. Other techniques which may be employedinclude, but are not limited to, dipping the frame 30 into a molten orotherwise unset coating material to coat the frame 30 or spraying theframe 30 with a molten or otherwise unset coating material to coat theframe 30. In such implementations, the coating material may besubsequently set, such as by cooling or chemical means, to form thecoating. Such alternative techniques, to the extent that they mayinvolve high temperatures, may include thermally protecting whateveroptical components are present, such as by using beryllium copper orother suitable materials to prevent heat transfer through the windowsassociated with the optical components, as discussed above.

The frame 30 may be covered by other techniques as well. For example,the covering material 50 may be a sheet, a sleeve, or a film materialwhich is applied to the frame. Such a covering material 50 may bebonded, such as with an adhesive material, or mechanically fastened tothe frame 30. For instance, a suitable film material may be an extrudedor laminated film that is adhesively or mechanically bonded to the frame30. Likewise, a suitable sheet material may be a single or multi-layersheet material that is adhesively or mechanically bonded to the frame30. Other exemplary covering material 50 include cast, foamed, orextruded materials suitable for attachment to the frame 30.

By such techniques, the frame 30, as well as the optical components andassociated circuitry where desired, may be encased in a coveringmaterial 50 to form an integral or unitary assembly with no exposed orexternal moving parts of the internal frame 30. For example, as depictedin FIG. 5, the sensor 10 includes features of the underlying internalframe 30 that are now completely or partially covered, such as theovermolded emitter housing 52 and detector housing 54.

In one implementation, the covering material 50 is a thermoplasticelastomer or other conformable coating or material. In such embodiments,the thermoplastic elastomer may include compositions such asthermoplastic polyolefins, thermoplastic vulcanizate alloys, silicone,thermoplastic polyurethane, and so forth. As will be appreciated bythose of ordinary skill in the art, the overmolding composition mayvary, depending on the varying degrees of conformability, durability,wettability, or other physical and/or chemical traits that are desired.

Furthermore, the covering material 50 may be selected based upon thedesirability of a chemical bond between the internal frame 30 and thecovering material 50. Such a chemical bond may be desirable fordurability of the resulting sensor 10. For example, to preventseparation of the covering material 50 from the internal frame 30, acovering material 50 may be selected such that the covering material 50bonds with some or all of the internal frame 30. In such embodiments,the covering material 50 and the portions of the internal frame 30 towhich the covering material 50 is bonded are not separable, i.e., theyform one continuous and generally inseparable structure.

Furthermore, in embodiments in which the covering material 50 employedis liquid or fluid tight, such a sensor 10 may be easily maintained,cleaned, and/or disinfected by immersing the sensor into a disinfectantor cleaning solution or by rinsing the sensor 10 off, such as underrunning water. In particular, such an covered sensor assembly may begenerally or substantially free of crevices, gaps, junctions or othersurface irregularities typically associated with a multi-partconstruction which may normally allow the accumulation of biologicaldetritus or residue. Such an absence of crevices and otherirregularities may further facilitate the cleaning and care of thesensor 10.

In the depicted example, flexible regions 38 of the frame 30incorporated into the sensor 10 (in either coated or uncoatedembodiments) provide vertical and/or lateral accommodation of a fingeror other patient digit, and thereby providing a conforming fit.Furthermore, in the depicted embodiment, the lateral sides of the frame30 (or the covering material 50 disposed over such lateral sides)facilitate the exclusion of environmental or ambient light from theinterior of the sensor 10. The lateral sides of the sensor 10,therefore, help prevent or reduce the detection of light from theoutside environment, which may be inappropriately detected by the sensor10 as correlating to the SaO₂. Thus, the pulse oximetry sensor maydetect differences in signal modulations unrelated to the underlyingSaO₂ level. In turn, this may impact the detected red-to-infraredmodulation ratio and, consequently, the measured blood oxygen saturation(SpO₂) value. The conformability of the fit of sensor 10 and thepresence of the lateral sides on the sensor 10, therefore, may helpprevent or reduce such errors.

While the frame 30 in the first configuration 28 may be used to form acovered or uncovered sensor 10, other frame configurations may also beused in accordance with the present technique. For example, referringnow to FIGS. 6-8, a second frame configuration 58 is depicted. Theexemplary second frame configuration 58 includes components noted abovewith regard to the first configuration 28, such as a symmetric pair offlexible regions 38, an emitter housing 34, and a detector housing 36,as well as a cable guide 60.

In the embodiment depicted in FIGS. 6-8, the second configuration 58 ofthe frame 30 is provided as a semi-rigid, generally annular structureupon which the emitter housing 34 and detector housing 36 are disposedopposite one another. Between the emitter housing 34 and detectorhousing 36, a symmetric pair of flexible regions 38 (as discussed withregard to FIGS. 2-4) is disposed. The flexible regions 38 function asdiscussed above, allowing the emitter housing 34 (and associated emitter22) and detector housing 36 (and associated detector 24) to moverelative to one another along the optical axis 44. In this manner,alignment of optical components, such as an emitter 22 and detector 24may be maintained while obtaining a conforming fit to a patient's digit.While the second configuration of FIG. 6 is depicted with one pair ofsymmetrical flexible regions 38, one of ordinary skill in the art willappreciate that additional flexible regions 38 may be provided on thesecond configuration 58 of the frame 30 to maintain optical alignment ofthe emitter 22 and detector 24.

Referring now to FIG. 7, the second configuration 58 of the frame 30 isdepicted as expanded along the optical axis 44 between the emitter 22and detector 24, such as to accommodate a large finger or toe needinggreater vertical space. The paired, symmetric flexible regions 38constrain the range of motion of the emitter 22 and detector 24 tolinear motion along the optical axis 44, thereby maintaining the emitter22 and detector 24 in alignment despite there motion relative to oneanother. Similarly, in FIG. 8, the second configuration 58 is depictedas collapsed along the optical axis 44, such as to accommodate a smallerfinger or toe, while maintaining alignment of the emitter 22 anddetector 24 along the optical axis 44.

The second configuration 58 of the frame 30 is depicted as covered inFIG. 9. The techniques and materials that may be used to cover thesecond configuration 58 of the frame 30 are the same or similar to thosediscussed above with regard to the covered first configuration 28 offrame 30 discussed in relation to FIG. 5. Likewise the coveredstructures and benefits are the same or similar to those discussed abovewith regard to the covered configuration of FIG. 5. In this manner, aunitary sensor or sensor body may be constructed about the secondconfiguration 58 of the frame 30 that provides a conforming fit whilemaintaining the optical alignment of the optical components.

Other frame configurations incorporating aspects of the presenttechnique are also possible. For example, referring now to FIGS. 10-12,a third frame configuration 66 is depicted. The exemplary third frameconfiguration 66 includes components noted above with regard to thefirst and second configurations 28 and 58, such as symmetric pairs offlexible regions 38, an emitter housing 34, and a detector housing 36.

In the embodiment depicted in FIGS. 10-12, the third configuration 66 ofthe frame 30 is provided as a hinged, loop structure upon which theemitter housing 34 and detector housing 36 are disposed opposite oneanother. Between the emitter housing 34 and detector housing 36, foursymmetric pairs of flexible regions 38 is disposed. The flexible regions38 function as discussed above, allowing the emitter housing 34 (andassociated emitter 22) and detector housing 36 (and associated detector24) to move relative to one another along the optical axis 44. In thismanner, alignment of optical components, such as an emitter 22 anddetector 24 may be maintained while obtaining a conforming fit to apatient's digit. While the third configuration of FIG. 10 is depictedwith four pairs of symmetrical flexible regions 38, one of ordinaryskill in the art will appreciate that less than or more than fourflexible regions 38 may be provided on the third configuration 66 of theframe 30 to maintain optical alignment of the emitter 22 and detector24.

Referring now to FIG. 11, the third configuration 66 of the frame 30 isdepicted as expanded along the optical axis 44 between the emitter 22and detector 24, such as to accommodate a large finger or toe needinggreater vertical space. The paired, symmetric flexible regions 38constrain the range of motion of the emitter 22 and detector 24 tolinear motion along the optical axis 44, thereby maintaining the emitter22 and detector 24 in alignment despite there motion relative to oneanother. Similarly, in FIG. 12, the third configuration 66 is depictedas collapsed along the optical axis 44, such as to accommodate a smallerfinger or toe, while maintaining alignment of the emitter 22 anddetector 24 along the optical axis 44.

The third configuration 66 of the frame 30 is depicted as covered inFIG. 13. The techniques and materials that may be used to cover thethird configuration 66 of the frame 30 are similar to those discussedabove with regard to the covered first configuration 28 of frame 30discussed in relation to FIG. 5. Likewise the covered structures andbenefits are the same or similar to those discussed above with regard tothe covered configuration of FIG. 5. In this manner, a unitary sensor orsensor body may be constructed about the third configuration 66 of theframe 30 that provides a conforming fit while maintaining the opticalalignment of the optical components.

While the exemplary medical sensors 10 discussed herein are provided asexamples, other such devices are also contemplated and fall within thescope of the present disclosure. For example, other medical sensorsand/or contacts applied externally to a patient may be advantageouslyapplied using an covered sensor body as discussed herein. Examples ofsuch sensors or contacts may include glucose monitors or other sensorsor contacts that are generally held adjacent to the skin of a patientsuch that a conformable and comfortable fit is desired. Similarly, andas noted above, devices for measuring tissue water fraction or otherbody fluid related metrics may utilize a sensor as described herein.Likewise, other spectrophotometric applications where a probe isattached to a patient may utilize a sensor as described herein.

Furthermore, though the preceding discussion notes the possibility ofcovering the frame 30 with an overmold material to construct the sensor10 or the sensor body, one of ordinary skill in the art will appreciatethat the frame 30 may also be used without such a covering. For example,the frame 30 may itself form a sensor body, with optical components suchas the emitter 22 and/or detector 24 being added to the frame 30 to formthe sensor 10. In such an embodiment, an adhesive strip or bandage mayhelp secure the sensor 10 to the patient.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims. Indeed, the present techniques may not only be appliedto transmission type sensors for use in pulse oximetry, but also toretroflective and other sensor designs as well. Likewise, the presenttechniques are not limited to use on fingers and toes but may also beapplied to placement on other body parts such as in embodimentsconfigured for use on the ears or nose.

1. A sensor assembly, comprising: a frame comprising one or more pair offlexible elements disposed substantially symmetric relative to anoptical axis; at least two optical components disposed on the framealong the optical axis; and a covering provided over at least part ofthe frame and the at least two optical components.
 2. The sensorassembly of claim 1, wherein the frame comprises two or more partsjoined to form the frame.
 3. The sensor assembly of claim 1, wherein thecovering comprises a thermoplastic elastomer.
 4. The sensor assembly ofclaim 3, wherein the thermoplastic elastomer comprises at least one of athermoplastic polyolefin, a thermoplastic vulcanizate alloy,thermoplastic polyurethane, silicone, or a combination thereof.
 5. Thesensor assembly of claim 1, wherein the covering comprises a flexiblesheet, a sleeve or a film material.
 6. The sensor assembly of claim 1,wherein the covering is bonded to the frame.
 7. The sensor assembly ofclaim 1, wherein the covering is mechanically fastened to the frame. 8.The sensor assembly of claim 1, wherein the covering comprises a cast,foamed, or extruded material.
 9. The sensor assembly of claim 1, whereinno moving parts of the frame remain exposed from the covering.
 10. Thesensor assembly of claim 1, comprising at least one integrated circuitdevice.
 11. The sensor assembly of claim 1, wherein the one or more pairof flexible elements comprise one or more pair of living hinges, pinhinges, bar links, or bending beams.
 12. A sensor assembly, comprising:a frame; an emitter and a detector housed on the frame along an opticalaxis, wherein the emitter and the detector are configured to moverelative to one another while remaining aligned along the optical axis;and a covering provided over the frame, the emitter, and the detector.13. A method of manufacturing a sensor, comprising: situating an emitterand a detector on a frame, wherein the frame comprises one or more pairof flexible elements disposed substantially symmetric relative to anoptical axis upon which the emitter and the detector are situated; andcoating the frame with a coating material to form a sensor assembly. 14.A method for acquiring physiological data, comprising: emitting two ormore wavelengths of light from an emitter of a sensor assembly disposedon a patient; detecting transmitted or reflected light using aphotodetector of the sensor assembly, wherein the emitter and thephotodetector are maintained in optical alignment with one another alongan optical axis by one or more pair of flexible elements of the sensorassembly, wherein the one or more pair of flexible elements are disposedsymmetrical to the optical axis; and determining a physiologicalparameter based on the detected light.
 15. A method of manufacturing asensor body, comprising: coating a frame with a coating material to forma sensor body, wherein the frame comprises one or more pair of flexibleelements disposed substantially symmetric relative to an optical axisdefined by an emitter housing and a detector housing of the frame.
 16. Asensor body, comprising: a frame comprising one or more pair of flexibleelements disposed substantially symmetric relative to an optical axisdefined by an emitter housing and a detector housing of the frame; and acovering provided over the frame.
 17. A sensor body, comprising: a framecomprising an emitter housing and a detector housing which define anoptical axis, wherein the emitter housing and the detector housing areconfigured to move relative to one another while remaining aligned alongthe optical axis; and a covering provided over the frame to form asensor assembly.
 18. A frame of a sensor, comprising: at least twooptical component housings defining an optical axis; and one or morepair of flexible elements disposed substantially symmetric relative tothe optical axis.
 19. A frame of a sensor, comprising: an emitterhousing and a detector housing which define an optical axis, wherein theemitter housing and the detector housing are configured to move relativeto one another while remaining aligned along optical axis.
 20. A methodfor manufacturing a frame of a sensor, comprising: forming at least twooptical component housings of a frame of a sensor such that the at leasttwo optical component housings define an optical axis; and providing oneor more pair of flexible elements on the frame disposed substantiallysymmetric relative to the optical axis.